Tinzaparin. A review of its pharmacology and clinical potential in the prevention and treatment of thromboembolic disorders.

Tinzaparin, a low molecular weight (LMW) heparin with an average molecular weight of 4.5 +/- 1.5 kD, has greater bioavailability and a longer duration of action than unfractionated heparin, allowing it to be administered once daily by subcutaneous injection for both prophylaxis and treatment of deep venous thrombosis (DVT). Like other members of its class, tinzaparin has a greater ratio of antifactor Xa/anti-factor IIa activity than unfractionated heparin, providing the theoretical advantage of similar antithrombotic efficacy with a diminished risk of haemorrhagic complications. In a small number of clinical trials, tinzaparin was found to be more effective than intravenous dextran or oral warfarin sodium as prophylaxis against DVT in high-risk patients undergoing orthopaedic surgery, and more effective than subcutaneous heparin in both general surgical patients and medical patients with an immobilising illness. When used for the treatment of established DVT, tinzaparin was more effective in preventing DVT recurrence than intravenous heparin, both initially and during a 3-month follow-up period when patients received warfarin sodium. Tinzaparin was also used successfully in one small study to maintain the patency of haemodialysis circuits over a 6-month period, with favourable effects on the lipid profile of such patients. Tinzaparin is well tolerated, the most frequent complication being injection site haematoma. In comparative trials, tinzaparin was associated with fewer major haemorrhagic complications than intravenous heparin (when used for treatment of venous thrombosis), but more than warfarin sodium. Other adverse events which have been reported in tinzaparin-treated patients include elevated liver enzyme levels and thrombocytopenia. Thus, although clinical experience is limited at present, available data suggest that, in common with other LMW heparins, tinzaparin is likely to prove an effective alternative to unfractionated heparin for both the prevention and treatment of DVT, with the advantage of more convenient administration and decreased monitoring requirements.